Clearing water surfaces of oil



Patented Aug. 24, 1948 CLEARINGIWATER SURFACES OFOIL William-A. Zisman,Washington,- D*."C., and-Lamar Pickett, Arlington, Va.

No Drawing. Application-.June22, 15143,, Serial No. 491,838!

(Granted under the. act of..March.3, 1883, as amended April 30, 1928.;.370 0.;Gfl'757) 4 Claims.

Thisinvention relatestoa method of clea n water surfaces of oil. and tocompositions used therewith. In particular the invention is concernedwith theprotection oi the crews of torpedoed or sinking ships where fueloil or gasoline from,the ship has spread over the water.

Thefuel oils,,lubricating oils and the gasoline escaping from a bombed..or torpedoed ship or storage -.tankoften spread out over the waterforming ..a.layer or blanket which may be anywhere fromless than athousandth. of. an inchto many inchesdeep, depending on the viscosity oftheoiLthe amount of escapingoil and the efiects of the wind. If the oilfilm .is of .the orderof a thousandth of an inch thick it is not aserious menace.since. it-is. kept cool by the water underneath, althoughit may cause discomfort to swimmers. Onthe other hand, films or blanketsonly one-fourth of an inch thick are a fire hazard and 'evenwhen notburning they tend to blind and suffocate swimmers.

This inventionxprovides a method of clearing limitedareas of watersurfaces of oil where the original-oil film or layer is not greaterthanabout one-fourth-to one-half inch thick, and it is especiallyadapted "to the protection of swimmers .and

survivors in life boats or on rails by holding the oil film 'at adistance. The lengthier time which-the oil -film"may be held at baydepends largely on the weather prevailing at the time, as. rough weathertends tocounteract the effects of the method. However, moderate windstend to blow the oil film away from the vessel so that there is a betterchance of escape by leaving from the windward side, whereas in calmweather the oil tends to form a blanket or pool equally extensive in alldirections about the ship. It is under the latter circumstances that themethod of this invention is most efficacious. The invention alsoincludes certain compositions of matter used in repelling the oil film.

The principle of the invention resides in the use of certain agents torepel the oil when they are applied to the water. Those agents arecertain polar organic compounds which are insoluble or slightly solublein water and which therefore spread out over the water surface in aninvisible layer one molecule thick. In addition the compounds areinsoluble or nearly so in fuel oils, gasoline and the like, they are notharmful to human beings and they have unusually high spreadingpressures, the latter enabling them to repel oil layers of thicknessesof the order of onefourth to one-half inch. Another essentialcharacteristic of these compounds is the fact that the 2;. are liquid.(1. e., notsolid). andalsomaintain high spreading-pressures\attemperatures ashlow as 40 F., thusenabling them to operateefiectively-in.co1d .waters.

The compounds used in this .inventionare liquid esters of. higher .fattyacidsand .hydroxy compounds selected-from. the group; consisting. ofsugars and sugar derivatives. In partic'ularesters ofoleiciandricinoleic acidsare most, suitable-because they remainliquidat lowtemperatures,

andthe esters of-these acidswhich show the greatest oil. and water.insolubilityland highest spreading pressures are .those vof .sorbitoland mannitoland derivatives. of sorbitol .andmannitol. Particularlydesirable compounds include scrbitan monooleate, sorbitanmonoricinoleate, sorbitan trioleate, modified. sorbitan. I.diricinoleate, monolaurate .andhexaricinoleate, modified mannitan.monooleate and mannidemonooleate... The

spreading pressures .of -.these.compounds. invdynes percentimeter,measuredat. the boundary line of the oilIfilm,is given. inthefo'llowing table.

Tl'ible Spreading.

pressure Compound sorbitan monooleate 40. 6 46. 5 modified sorbitandiricinoleate 34. 3 37:4 modified sorbitmmouolaunate 3t 8 37. 3 sorbitanmonoricinoleate 34.3 36:8 modifiedmannitan monooleate' 39:0 37. '5sorbitan trioleate 36. 8 35. 6 modified sorbitan hexariciuoleate. 33. 837. 6 mannide monooleate 37. 0 39. 0

The esters shown above are all derivatives of sorbitol and mannitol. Thesorbitans and mannitans are the products obtained by removing onemolecule of water from sorbitol and mannitol, forming an internal etherlinkage or lactone ring in the molecule, and the sorbides and mannidesare the products resulting from the removal of two molecules of waterfrom sorbitol and mannitol, respectively. Since sorbitol and mannitolare hexahydroxy compounds, it is obvious that the sorbitans andmannitans have four hydroxy groups available for esterification or otherreaction, and the sorbides and mannides have two available hydroxyls.The modified esters listed in the table were those in which one or morehydroxyls of the sorbitan or mannitan not used in ester linkage werereacted with polyalkylene oxides to give polyoxyalkylene side chains tothe ester. This side chain renders the ester less oil soluble and morewater soluble.

It is obvious that mixtures of the above have almost any desiredcharacteristics of oil and/or water solubility (or insolubility), toyield spreading agents of maximum efiiciency. In fact the compoundsemployed in the above tests contained small amounts of other similaresters inasmuch as they were of commercial grade when used, rather thanchemically pure.

the United States of America for governmental purposes without thepayment of any royalties thereon or therefor.

I claim:

1. A method of opening an oil-free area in a water surface oil blanketnot exceeding one-half inch in thickness comprising impelling the oilfrom the area into the surrounding region by In use the ester is appliedto the water either life jacket, as only a relatively small amount is.

needed.

Tests with the esters listed in the table showed them capable of holdingback a one-fourth inch wall of fuel oil on a water surface for overtwentyfour hours without apparent diminution of strength. These testswere made under ideal conditions, so that further tests were undertakenat sea. With a Wind velocity of a few miles per hour and calm sea at atemperature of about 48 F., a puddle of oil amounting to between 800 and900 gallons spreading over a circular area about 300 yards in diameterwas forced back from a spot in its center to a distance of about 35 feetfrom the ship by dumping about two gallons of a 25% solution of theester in hexanol into the water. Where the oil layer was churned by thepropeller the effect of the ester was quite evident in assistingbreaking the oil up into small discs which floated on the water ratherthan emulsified with it.

For individual use in swimming in the sea the ester is better applied inconcentrated form to the water surface by means of a sponge or otherabsorbent material soaked in the ester, or it may be applied from acollapsible tube, as only a few ounces per person are necessary.However, prolonged contact of the ester with the filling in life jacketsshould be avoided because the buoyancy of the latter is adverselyaffected in time. Of course the esters have no such effect on inflatabletypes of life rafts and preservers.

Many variations will be apparent to those skilled in the art, and theinvention should not be limited other than as defined by the appendedclaims.

The invention described herein may be manufactured and used by or forthe Government of introducing to the water surface at a positio withinsaid blanket a solution of a compound selected from the group consistingof sorbitan monooleate, sorbitan monoricinoleate and mannide monooleate,the said solution consisting of about twenty-five percent by weight ofsaid compound dissolved in a solvent selected from the group consistingof hexanol and octanol.

2. The method as defined in claim 1 in which the solution introduced tothe water surface within said blanket consists of about twenty-fivepercent by weight of sorbitan monooleate dissolved in ,a solventselected from the group consisting of hexanol and octanol.

3. The method as defined in claim 1 in which the solution introduced tothe water surface within said blanket consists of about twenty-fivepercent by weight of mannide monooleate dissolved in a solvent selectedfrom the group consisting of hexanol and octanol.

4. The method as defined in claim 1 in which the solution introduced tothe water surface within said blanket consists of about twenty-fivepercent by weight of sorbitan monoricinoleate dissolved in a solventselected from the group consisting of hexanol and octanol.

WILLIAM A. ZISMAN. LAMAR PICKETT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,950,937 Brown Mar. 13, 19342,017,868 Nolan Oct. 22, 1935 2,285,422 Epstein et a1. June 9, 19422,322,820 Brown June 29, 1943 2,322,822 Brown June 29, 1943 OTHERREFERENCES Spans and Tweens, Booklet of Atlas Powder Co. (1942), pages7, 8, 11 and 16.

